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E90/E91/E92/E93 (2006 - 2013) The E9X is the 4th evolution of the BMW 3 series including a highly tuned twin turbo 335i variant pushing out 300hp and 300 ft. lbs. of torque. BMW continues to show that it sets the bar for true driving performance! -- View the E9X Wiki

You're RIGHT. Just checked some cars from cars.com and all have N51 engine

Is this a good thing or no? Not sure how this will impact my modification list

I think the jury is still out on whether the N51 or the N52 is the better engine. The BMW claimed horsepower, torque, and performance are the same.

The N51 has some specialized low-emissions components. These could potentially be expensive in the future. But the emissions warranty on the N51 is either 120,000 or 150,000 miles, depending on the component. The N51 emissions warranty also is more comprehensive than the N52 emissions warranty. Overall, there does not seem to be a compelling reason to prefer one engine over the other.

On the E46 (previous generation 3-Series), the SULEV version (M56 engine) had a completely sealed fuel system, with no serviceable parts. Therefore, when the fuel pump failed, the entire fuel tank and system had to be replaced, at a cost of about $8000. Obviously, this is something buyers wish to avoid.

On the E90, all components (fuel pump, etc.) are individually replaceable. So theoretically, there is no post-warranty "ticking timebomb".

On the E46 (previous generation 3-Series), the SULEV version (M56 engine) had a completely sealed fuel system, with no serviceable parts. Therefore, when the fuel pump failed, the entire fuel tank and system had to be replaced, at a cost of about $8000. Obviously, this is something buyers wish to avoid.

On the E90, all components (fuel pump, etc.) are individually replaceable. So theoretically, there is no post-warranty "ticking timebomb".